Some related art methods of taking digital power measurements use non-rectified input current and input voltage. The directly measured signals are then converted from analog to digital, allowing a microprocessor to calculate average power using root-mean-square current and voltage.
Other related art methods use primary side input power which can be measured for power factor correcting (PFC) power supplies. Rectified input voltage and current to the PFC stage are measured using a current sensor and voltage sensor. A correction factor is applied to compensate for any phase shift introduced by current sensing.
Still other related art methods use the input power of a power factor correcting power supply, which can be measured, by monitoring only the output current of the power supply at a known output voltage level. A look up table or correction factor is applied, using previously known operating parameters, to extrapolate the input power. Output power is divided by the known efficiency value of the input section.